How to fix a cat's missing teeth:
1. After a cat loses a tooth, you should have its teeth cleaned regularly, and then apply some antibiotics to prevent infection.
2. If it is caused by periodontitis or other dental diseases, you need to give your dog medication to reduce inflammation and clean its mouth. It should receive special treatment as soon as possible, so you should take it to the vet as soon as possible.
3. If it is a normal teething process for the cat, you need to provide chewy food to protect the new teeth. 
Reasons why cats lose their teeth:
1. A kitten's baby teeth usually fall out around 3 months old, and its new teeth will grow in by 5 to 6 months old. This is due to the teething period.
2. Around the age of 12, a cat's gums and gum line will begin to loosen and age, and its teeth will gradually fall out. This is a normal phenomenon.
3. Cats suffering from periodontitis or other oral diseases can experience loose teeth and tooth loss, accompanied by severe pain.
